Hemoglobin in blood is converted to glycated hemoglobin by reacting with glucose in blood. Among the various types of glycated hemoglobin, hemoglobin A1c (HbA1c), in particular, serves as an important indicator in the diagnosis, treatment, and the like of diabetes. HbA1c is hemoglobin A (HbA0) whose β-chain N terminal valine has been glycated. HbA1c is classified as stable hemoglobin A1c (hereinafter also referred to as “stable A1c” or “s-A1c”.) or labile hemoglobin A1c (hereinafter also referred to as “labile A1c” or “L-A1c”) according to the stage of the glycation reaction. Labile A1c is HbA0 that has been converted to aldimine by the binding of glucose to its β-chain N terminal valine through a Schiff base linkage. When the labile A1c further undergoes the Amadori rearrangement to become a ketoamine compound, it is called stable A1c. Stable A1c reflects the blood glucose level of the past few months in a subject. Stable A1c may be measured by a measurement method standardized by the Japan Diabetes Society.
Examples of methods for measuring glycated hemoglobin in blood include an immunization method, an enzyme method, affinity chromatography, HPLC, and capillary electrophoresis. The immunization method and the enzyme method are applicable to automated analyzers. Thus, these methods are advantageous in that they can treat a large number of specimens. However, the measurement accuracies of these methods are not sufficient to provide accurate measured values that can serve as blood sugar control indicators and/or complication onset prevention markers for diabetics. Affinity chromatography has low specificity for β-chain N-terminal glycated valine because of its separation principle, so that the measured value also includes the measured value of glycated lysine in Hb molecules. Thus, affinity chromatography results in a low accuracy for HbA1c measurement. HPLC is used widely as a method for measuring glycated hemoglobin in the treatment of diabetics (e.g., JP 3429709 B). However, it requires an expensive dedicated apparatus, and it is difficult to reduce the size and the cost of the apparatus. From the viewpoint of, for example, utilization in group medical examinations, there has been a demand for size reduction of hemoglobin analyzers. However, as described above, for HPLC, it is difficult to satisfy this demand.
On the other hand, in capillary electrophoresis, ions that have gathered on the inner wall of a capillary channel migrate when a voltage is applied, thus causing an electroosmotic flow. This causes the sample to migrate, whereby electrophoresis is performed. In capillary electrophoresis, the size of a capillary electrophoresis apparatus as a whole can be reduced by making the capillary channel shorter and/or configuring a part of the capillary electrophoresis apparatus as a microchip, for example. As a method for analyzing HbA1c according to capillary electrophoresis, a method using a capillary tube having an anionic layer laminated on its inner wall has been reported, for example (e.g., WO 2008/029684 A1 and WO 2008/029685 A1).